Dataset Information

Comprehensive molecular, genomic and phenotypic analysis of a major clone of Enterococcus faecalis MLST ST40.

ABSTRACT: BACKGROUND: Enterococcus faecalis is a multifaceted microorganism known to act as a beneficial intestinal commensal bacterium. It is also a dreaded nosocomial pathogen causing life-threatening infections in hospitalised patients. Isolates of a distinct MLST type ST40 represent the most frequent strain type of this species, distributed worldwide and originating from various sources (animal, human, environmental) and different conditions (colonisation/infection). Since enterococci are known to be highly recombinogenic we determined to analyse the microevolution and niche adaptation of this highly distributed clonal type. RESULTS: We compared a set of 42 ST40 isolates by assessing key molecular determinants, performing whole genome sequencing (WGS) and a number of phenotypic assays including resistance profiling, formation of biofilm and utilisation of carbon sources. We generated the first circular closed reference genome of an E. faecalis isolate D32 of animal origin and compared it with the genomes of other reference strains. D32 was used as a template for detailed WGS comparisons of high-quality draft genomes of 14 ST40 isolates. Genomic and phylogenetic analyses suggest a high level of similarity regarding the core genome, also demonstrated by similar carbon utilisation patterns. Distribution of known and putative virulence-associated genes did not differentiate between ST40 strains from a commensal and clinical background or an animal or human source. Further analyses of mobile genetic elements (MGE) revealed genomic diversity owed to: (1) a modularly structured pathogenicity island; (2) a site-specifically integrated and previously unknown genomic island of 138 kb in two strains putatively involved in exopolysaccharide synthesis; and (3) isolate-specific plasmid and phage patterns. Moreover, we used different cell-biological and animal experiments to compare the isolate D32 with a closely related ST40 endocarditis isolate whose draft genome sequence was also generated. D32 generally showed a greater capacity of adherence to human cell lines and an increased pathogenic potential in various animal models in combination with an even faster growth in vivo (not in vitro). CONCLUSION: Molecular, genomic and phenotypic analysis of representative isolates of a major clone of E. faecalis MLST ST40 revealed new insights into the microbiology of a commensal bacterium which can turn into a conditional pathogen.

SUBMITTER: Zischka M

PROVIDER: S-EPMC4374294 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Comprehensive molecular, genomic and phenotypic analysis of a major clone of Enterococcus faecalis MLST ST40.

Zischka Melanie M Künne Carsten T CT Blom Jochen J Wobser Dominique D Sakιnç Türkân T Schmidt-Hohagen Kerstin K Dabrowski P Wojtek PW Nitsche Andreas A Hübner Johannes J Hain Torsten T Chakraborty Trinad T Linke Burkhard B Goesmann Alexander A Voget Sonja S Daniel Rolf R Schomburg Dietmar D Hauck Rüdiger R Hafez Hafez M HM Tielen Petra P Jahn Dieter D Solheim Margrete M Sadowy Ewa E Larsen Jesper J Jensen Lars B LB Ruiz-Garbajosa Patricia P Quiñones Pérez Dianelys D Mikalsen Theresa T Bender Jennifer J Steglich Matthias M Nübel Ulrich U Witte Wolfgang W Werner Guido G

BMC genomics 20150312

<h4>Background</h4>Enterococcus faecalis is a multifaceted microorganism known to act as a beneficial intestinal commensal bacterium. It is also a dreaded nosocomial pathogen causing life-threatening infections in hospitalised patients. Isolates of a distinct MLST type ST40 represent the most frequent strain type of this species, distributed worldwide and originating from various sources (animal, human, environmental) and different conditions (colonisation/infection). Since enterococci are known ...[more]

PMID: 25887115

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Project description:Enterococcus faecalis is the most commonly isolated enterococcal species in clinical infection. This bacterium is notorious for its ability to share genetic content within and outside of its species. With this increased proficiency for horizontal gene transfer, tremendous genomic diversity within this species has been identified. Many researchers have hypothesized E. faecalis exhibits niche adaptation to establish infections or colonize various parts of the human body. Here, we hypothesize that E. faecalis strains isolated from the human bladder will carry unique genomic content compared to clinical strains isolated from other sources. This analysis includes comparison of 111 E. faecalis genomes isolated from bladder, urogenital, blood, and fecal samples. Phylogenomic comparison shows no association between isolation source and lineage; however, accessory genome comparison differentiates blood and bladder genomes. Further gene enrichment analysis identifies gene functions, virulence factors, antibiotic resistance genes, and plasmid-associated genes that are enriched or rare in bladder genomes compared to urogenital, blood, and fecal genomes. Using these findings as training data and 682 publicly available genomes as test data, machine learning classifiers successfully distinguished between bladder and non-bladder strains with high accuracy. Genes identified as important for this differentiation were often related to transposable elements and phage, including 3 prophage species found almost exclusively in bladder and urogenital genomes. E. faecalis strains isolated from the bladder contain unique genomic content when compared to strains isolated from other body sites. This genomic diversity is most likely due to horizontal gene transfer, as evidenced by lack of phylogenomic clustering and enrichment of transposable elements and prophages. Investigation into how these enriched genes influence host-microbe interactions may elucidate gene functions required for successful bladder colonization and disease establishment.

Project description:Enterococcus faecalis, a member of the natural microbiota of animal and human intestinal tracts, is also present as a natural contaminant in a variety of fermented foods. Over the last decade, E. faecalis has emerged as a major cause of nosocomial infections. We investigated the genetic diversity in 30 clinical and food isolates, including strains V583 and MMH594, in order to determine whether clinical and food isolates could be distinguished. Data were obtained using comparative genomic hybridization and specific PCR with a total of 202 probes of E. faecalis, selected using the available V583 genome sequence and part of the MMH594 pathogenicity island. The cognate genes encoded mainly exported proteins. Hybridization data were analyzed by a two-component mixture model that estimates the probability of any given gene to be either present or absent in the strains. A total of 78 genes were found to be variable, as they were absent in at least one isolate. Most of the variable genes were clustered in regions that, in the published V583 sequence, related to prophages or mobile genetic elements. The variable genes were distributed in three main groups: (i) genes equally distributed between clinical and dairy food isolates, (ii) genes absent from dairy food-related isolates, and (iii) genes present in MMH594 and V583 strains only. Further analysis of the distribution of the last gene group in 70 other isolates confirmed that six of the probed genes were always absent in dairy food-related isolates, whereas they were detected in clinical and/or commensal isolates. Two of them corresponded to prophages that were not detected in the cognate isolates, thus possibly extending the number of genes absent from dairy food isolates. Genes specifically detected in clinical isolates may prove valuable for the development of new risk assessment markers for food safety studies and for identification of new factors that may contribute to host colonization or infection.

Project description:Enterococci are the third leading cause of hospital associated infections and have gained increased importance due to their fast adaptation to the clinical environment by acquisition of antibiotic resistance and pathogenicity traits. Enterococcus faecalis harbours a pathogenicity island (PAI) of 153 kb containing several virulence factors including the enterococcal surface protein (esp). Until now only internal fragments of the PAI or larger chromosomal regions containing it have been transferred. Here we demonstrate precise excision, circularization and horizontal transfer of the entire PAI element from the chromosome of E. faecalis strain UW3114. This PAI (ca. 200 kb) contained some deletions and insertions as compared to the PAI of the reference strain MMH594, transferred precisely and integrated site-specifically into the chromosome of E. faecalis (intergenic region) and Enterococcus faecium (tRNAlys). The internal PAI structure was maintained after transfer. We assessed phenotypic changes accompanying acquisition of the PAI and expression of some of its determinants. The esp gene is expressed on the surface of donor and both transconjugants. Biofilm formation and cytolytic activity were enhanced in E. faecalis transconjugants after acquisition of the PAI. No differences in pathogenicity of E. faecalis were detected using a mouse bacteraemia and a mouse peritonitis models (tail vein and intraperitoneal injection). A 66 kb conjugative pheromone-responsive plasmid encoding erm(B) (pLG2) that was transferred in parallel with the PAI was sequenced. pLG2 is a pheromone responsive plasmid that probably promotes the PAI horizontal transfer, encodes antibiotic resistance features and contains complete replication and conjugation modules of enterococcal origin in a mosaic-like composition. The E. faecalis PAI can undergo precise intra- and interspecies transfer probably with the help of conjugative elements like conjugative resistance plasmids, supporting the role of horizontal gene transfer and antibiotic selective pressure in the successful establishment of certain enterococci as nosocomial pathogens.

Dataset Information

Comprehensive molecular, genomic and phenotypic analysis of a major clone of Enterococcus faecalis MLST ST40.

Publications

Comprehensive molecular, genomic and phenotypic analysis of a major clone of Enterococcus faecalis MLST ST40.

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